1. Field of the Invention
This invention relates to apparatus for feeding stock material intermittently to a press and more particularly to apparatus for generating intermittent feeding of the stock material by oscillating rotational movement of a driven feed roll through a preselected angle of rotation.
2. Description of the Prior Art
It is the conventional practice in high speed automatic press operations to feed a strip of stock material from a coil to the dies of the press for punching, stamping, cutting or the like at a preselected length of the stock material. The stock material must be fed from the coil in timed relation with the press operation so that before the dies contact the stock material, the stock material is moved into a final position by the die pilots as the feed rolls are released from engagement with the stock material. The stock material is then stationarily positioned between the dies. After the press operation is completed the feed rolls are actuated to advance another length of the stock material to the press. Therefore, the feeding of the stock material to the press must be coordinated with each press operation so that prior to each operation a new segment of stock material is in position relative to the dies for the press.
U.S. Pat. Nos. 4,133,216 and 4,138,913 are examples of one type feeding apparatus for power punch presses in which the feed rolls are drivingly connected by a plurality of meshing gears to an input shaft drivingly connected to the punch press crankshaft. A gear cammed drive receives continuous, uniform rotation from the input shaft and converts the rotation to a noncontinuous step-by-step, intermittent rotational movement to the driven feed roll. With this arrangement the feed rolls advance intermittently through a 360.degree. rotational cycle. During the dwell periods of the rotational cycle the driven feed roll is not rotated and the punching operation is carried out. After the punching operation is completed, the feed rolls are again incrementally advanced so that another preselected length of stock material is passed beneath the press.
U.S. Pat. Nos. 3,758,011 and 3,784,075 are examples of another type of incremental feed apparatus that converts continuous rotation of a drive shaft to contrarotating oscillating movement of the feed rolls. The drive shaft is connected through a pair of meshing gears one of which is arranged eccentrically and is connected to a lever that is rotated to-and-fro. The pivotal movement of the lever is transmitted to a shaft that is, in turn, coupled to the feed rolls. The oscillatory movement of the lever and shaft is transmitted to the feed rolls to generate a to-and-fro movement. The feed length can be changed by altering the amplitude of the oscillatory movement of the feed rolls.
Synchronously with the to-and-fro movement of the feed rolls, the feed rolls move toward one another into a feed position and move away from one another into an idling position. The movement of the feed rolls between the feed and idling positions takes place at the point where the feed rolls change directions of oscillation. A holding mechanism for the workpiece is actuated when the feed rolls move from their feed position into the idling position and is deactuated when the rollers move from their idling position into the feed position.
There is need for press feeding apparatus that incrementally feeds the workpiece to the press by oscillatory movement of a feed roll generated by the rotation of the press crankshaft in an arrangement that permits precise adjustments to be made in the feed length. While it has been suggested to oscillate the feed rolls of a press feed to incrementally feed the workpiece to the press, the prior art feeding apparatus require a complex arrangement for interconnecting the operations of feeding, clamping, and releasing the feed rolls the requires many component parts which necessitate increased maintenance and replacement of worn parts.